Radio receiver



May 1937- N s. MARKUS ET AL 2,079,655

RADIO RECEIVER Filed May 14, 1955 INVENTORS N. S. MARKUS M.J.O. STRUTT ATTORNEY.

Patented May" 11, 1937 UNITED STATES PATENT OFFICE RADIO RECEIVER Netherlands Application May 14,

1935, Serial No. 21,352

In Germany June 6, 1934 4 Claims.

The invention relates to a radio receiving or circuit arrangement in which a multi-grid tube is utilized for the rectification or modulation and simultaneously for the production of high-frequency oscillations, more particularly to those circuit arrangements wherein one of the grid circuits comprises an oscillatory circuit in which owing to the reactive coupling of another grid or to the presence of a negative resistance, oscillations are produced and wherein the electrodes which serve to produce oscillations are located in closer proximity to the cathode than the grid to which a variable bias is applied in order to regulate the amplification.

Such a circuit arrangement is represented in Figure 1 of the accompanying drawing. This figure represents a discharge tube T comprising a cathode K and an anode A between which a plurality of grids I, 2, 3, 4, 5 and 6 are located. The grid 4 is connected to a circuit 1 to which the received oscillations are supplied. The connecting lead between the grid 4 and the cathode comprises furthermore a resistance 8. The voltage drop produced, in said resistance serves to regulate the amplification and is preferably determined by the amplitude of the received carrier oscillations. The local oscillations are produced in a circuit 9 which is connected to the grid I through a grid condenser Ill with a leakage resistance II. The grid electrode 2 which acts as an anode for producing oscillations and which hereinafter will be referred to as oscillator anode, is connected to the source of anode voltage through a retroaction coil I2 and a resistance l3 0 bridged by a condenser l4. The retroaction coil i2 is coupled to the inductance of the circuit 9 so that in the latter oscillations are produced. The anode A is connected to the source of anode voltage through a circuit l5 which is tuned to the intermediate frequency desired. The screen grids 3 and 5 are conductively connected to one another either inside or outside the tube and are connected to asource of anode voltage through a resistance IS in parallel with a condenser ll. The grid 6 is conductively connected to the cathode as shown.

It has been found that when in the circuit arrangement described due to the increase of the voltage drop in the resistance 8 depending on the amplitude of the carrier oscillation received, the bias potential of the grid 4 becomes more negative, the amplitude of the local oscillations increases and furthermore the frequency thereof varies.

The invention has for its object to provide a circuit arrangement in which the amplitude and the frequency of the local oscillations are constant.

According to the invention, this is achieved by applying a variable portion of the bias volt age for regulating the amplification to one or. more of the oscillator electrodes or screen grids or to both these kinds of electrodes of the multigrid tube.

One mode of realization of the circuit arrangement according to the invention is shown in Figure 2 in which the negative terminal of the source of anode voltage 20 is connected as by a sliding contact to an adjustable point I8 of the resistance 8 so that a portion of the variable voltage supplied to the resistance 8 is applied to the oscillator anode 2, the screen grids 3 and 5 and the anode A. It has been found that an exact adjustment of the point l8 of the resistance 8 renas novel and desire to secure by Letters Patent is: 2

1. In a combined oscillator and detector device, the combination of an electron discharge tube having a cathode, an oscillator grid, an oscillator anode, a signal grid and a plate arranged in the order named, an input circuit including a coil shunted by a condenser and tunable to the signal frequency, a resistor having one end connected to the lower end of said coil and its other end to said cathode, the upper end of said coil being directly connected to said signal grid; a second coil shunted by a condenser and resonant to a local oscillation frequency, a direct connection between one end of said second coil and said cathode, a circuit including a series resistor connecting the other end of said second coil and said oscillator grid, a condenser shunted across said resistor, a source of positive potential, a circuit including the series connection of a third coil and a resistor connecting the positive terminal of said potential source and said oscillator anode, said third coil being inductively coupled to said second coil, a circuit connecting the negative terminal of said potential source to said cathode and a circuit connecting the positive terminal of said potential source and said plate and including a portion res- I onant to the intermediate frequency.

2. In a combined oscillator and detector device, an electron discharge tube having a cathode, a plate and a plurality of grids located between said plate and cathode, a circuit tuned to the heterodetector, a vacuum tube having a cathode, a plate, and an oscillator grid, an oscillator grid-anode,

and a signal grid arranged between said cathode and plate in the order named, a circuit tuned to a local oscillation frequency connected to said oscillator grid and cathode, a source of potential,

a circuit conductive to direct current connected 20 to the positive terminal of said potential source and said grid-anode and including a feedback connection to said last named circuit, an output circuit connected to said plate and the positive terminal of said potential source, a circuit connected to said signal grid and cathode and including the series connection of a fixed resistor and a reactance tunable to the signal frequency, a contact adjustable along said resistor and a direct current connection between said contact and '-ode and plate, a circuit tuned to a local oscillation frequency connected to said oscillator grid and cathode, a source of potential, a circuit conductive to direct current connected to the positive terminal of said potential source and said gridanode and including a feedback connection to said last named circuit, an output circuit connected to said plate and including a portion tuned to the intermediate frequency, a circuit connected to said signal grid and cathode and including a portion tunable to an incoming signal frequency, and a. single adjustable control means arranged to decrease the direct current potential of said signal grid and to also decrease the direct current potential' difierence between said grid-anode and said cathode whereby the frequency of the locally generated oscillations remains substantially constant upon adjustment of said control means.

NOLKE SIEDS MARKUS.

MAXIMILIAAN JULIUS OTTO STRUTT. 

